A chain transmission device includes a driving sprocket mounted to a crankshaft, a driven sprocket mounted to a camshaft, and a timing chain trained around the driving sprocket and the driven sprocket and configured to drive the camshaft. Such a chain transmission device further includes a chain guide provided on one side of the slack side of the timing chain and pivotable about a first end thereof, and a chain tensioner configured to apply an adjusting force to a second end of the chain guide remote from the first end so as to apply tension to the timing chain, thereby preventing the chain from slackening and flapping.
Typically, such a chain transmission device further includes a fixed chain guide provided along the tension side of the timing chain to guide the movement of the timing chain, thereby further reducing flapping of the chain.
Such chain guides, used to adjust tension or guide movement, of the timing chain, include those of the type which guide the timing chain by sliding surface contact with the timing chain. This type of chain guides, however, have a problem in that they offer a large moving resistance to the timing chain, thus increasing transmission torque loss.
The applicant proposed a chain guide in the below-identified Patent document 1 which is free of this problem. This chain guide includes a guide base elongated in the travel direction of the timing chain, and a plurality of roller shafts arranged along a curved line and having their both ends supported by the guide base. Rollers in the form of roller element bearings are rotatably supported by the respective roller shafts so that the timing chain is movably supported by the rollers.
This chain guide is advantageous in that since the timing chain is guided by the rollers with the rollers rolling, the chain guide hardly offers a moving resistance to the timing chain, thus minimizing transmission torque loss.